Observatory · the table
Where your atoms come from
Every element is a number: how many protons are in its nucleus. Hydrogen has one, helium two, and so on, one more at every step, to oganesson with 118. The universe began with only the first two and a trace of the third. Everything heavier was cooked later, in stars, in their explosions and collisions, and the last few in our own laboratories. Run the clock from the Big Bang to now and watch the table fill up.
The table, filling up
Fig. I. The table of the elements, each coloured by where it was made.
Click any element to see where it came from. In the first three minutes the young universe made hydrogen and helium, and a pinch of lithium, and then it was too cool and thin to do more. The first stars, a couple of hundred million years later, fused them into carbon, oxygen, silicon and the rest, up to iron, and the big ones blew it out into space when they exploded. Lithium, beryllium and boron are mostly chips knocked off heavier nuclei by cosmic rays. Iron itself comes largely from white dwarfs that grew too heavy and blew up.
Past iron, fusion costs energy, so the rest is built by adding neutrons. In old giant stars that happens slowly, over thousands of years, making about half of the heavy elements, barium and lead among them. The other half needs a flood of neutrons in seconds: colliding neutron stars, the source of most of the gold, platinum and uranium, as the chirp of 2017 showed. Switch to light → heavy for the plain order, one proton more at every step.
Why iron is the top
Fig. II. The binding energy of nuclei, with iron at the summit.
How tightly each particle in a nucleus is held, against the size of the nucleus. Going up the curve releases energy: that is fusion on the left, from hydrogen to helium to carbon to iron, and fission on the right, uranium splitting into middle-sized pieces. Iron and nickel sit at the top, the most tightly bound nuclei there are. A star that has made an iron core has nothing left to burn; that is the moment it collapses, as the life of a star shows.
Did you know…
Kryptonite, Superman's weakness, first turned up in the radio serial in 1943. In 2006 geologists in the Jadar valley in Serbia found a new mineral, and the Natural History Museum in London noticed its formula, sodium lithium boron silicate hydroxide, was the one written on the kryptonite case in Superman Returns, minus the fluorine. It was named jadarite. It is white, and not radioactive.
Vibranium, Wakanda's metal and Captain America's shield, soaks up the energy of a blow. No element can; real armour spreads a blow out over time and area instead, which is roughly what the comics ask of it.
Unobtainium, the floating superconductor of Avatar, started out as engineers' slang in the 1950s for the material a design would need and that did not exist. A superconductor that works at room temperature is still on every physicist's wish list.
Real, and stranger. One quarry in the village of Ytterby, near Stockholm, gave its name to four real elements: yttrium, ytterbium, terbium and erbium.
Who worked it out
Where it already matters
You. Apart from the hydrogen, almost every atom in you was made in a star: the carbon and oxygen, the calcium in your bones, the iron in your blood. The gold in a ring was most likely made in a neutron star collision before the Sun was born.
Caught in the act. In 1952 Paul Merrill found technetium in the light of red giant stars. Technetium has no stable form and its longest-lived kind lasts a few million years, so it could not have been there since the stars were born: they were making it now. Five years later Burbidge, Burbidge, Fowler and Hoyle laid out how stars make nearly all the elements, the paper the whole table above rests on.
The last ones. Everything past uranium is made by people, a few atoms at a time, in reactors and accelerators. Element 118 was confirmed in 2015; a handful of its atoms have ever existed, each for less than a thousandth of a second.